Chlorofluorocarbon (CFC) based chemicals have been widely use in industry in a variety of different applications including as refrigerants, aerosol propellants, blowing agents and solvents, among others. However, certain CFCs are suspected of depleting the Earth's ozone layer. Accordingly, more environmentally friendly substitutes have been introduced as replacements for CFCs. For example, 1,1,1,3,3-pentafluoropropane (HFC-245fa) is recognized as having favorable physical properties for certain industrial applications, such as foam blowing agents and solvents, and therefore is consider to be a good substitute for the CFCs previously used for these applications. Unfortunately, the use of certain hydrofluorocarbons, including HFC-245fa, in industrial applications is now believed to contribute to the global warming. Accordingly, more environmentally friendly substitutes for hydrofluorocarbons are now being sought.
The compound 1-chloro-3,3,3-trifluoropropene, also known as HCFO-1233zd or simply 1233zd, is a candidate for replacing HFC-245fa in some applications, including uses as blowing agents and solvents. 1233zd has a Z-isomer and an E-isomer. Due to differences in the physical properties between these two isomers, pure 1233zd (E), pure 1233zd (Z), or certain mixtures of the two isomers may be suitable for particular applications as refrigerants, propellants, blowing agents, solvents, or for other uses.
The compound 1,1,1,2,3-pentachloropropane (240fa) is a reactant useful in the production of both 245fa and 1233zd. Processes for making these compounds are well known in the art. See for example, U.S. Pat. Nos. 5,763,706 and 6,844,475. See also, U.S. Patent Publication No. 2011-0201853, which provides an integrated process and methods of producing 1233zd (E).
It has now been found that an important intermediate in the production of both 245fa and 1233zd, is an azeotrope or azeotrope-like mixture of 1,1,1,3,3-pentachloro-propane (240fa) and hydrogen fluoride (HF). This intermediate, once formed, may thereafter be separated into its component parts, for example, by extraction or distillation techniques. HCC-240fa has a boiling point of about 178.5° C. and HF has a boiling point of about 20° C. at standard atmospheric pressure. These azeotropic or azeotrope-like compositions find use not only as reactor feeds in the production of 245fa and 1233zd, but they are additionally useful as solvent compositions useful for removing surface oxidation from metals.